HAMR Slider Contact Detection via Thermal Oscillation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current contact detection methods for magnetic recording systems, particularly in heat-assisted magnetic recording (HAMR) devices with modulating air bearings, struggle to accurately detect head-disk contact due to saturation issues and increased risk of slider burnishing, especially at middle diameter locations.
Innovation Solution
A contact detection methodology that utilizes a DC biased contact sensor to measure the amplitude of a spike in the DC response signal and calculates a ratio with the dR/dP curve, allowing for early detection of head-disk contact by exceeding a predetermined threshold, thereby reducing repeated contact and slider burnishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional contact detection methods are used for HAMR devices with modulating air bearings, then the detection process is simple, but the accuracy of head-disk contact detection deteriorates due to saturation issues and increased risk of slider burnishing
Solution Approach 1:
The patent applies mechanical vibration by modulating the air bearing at a specific frequency (e.g., 100 Hz) to create oscillations in the slider-disk spacing. This vibration allows the detection system to identify contact events through characteristic changes in the contact sensor signal during the oscillation cycle, thereby improving contact detection accuracy while accounting for the modulating air bearing behavior that causes traditional methods to saturate
Solution Approach 2:
The patent implements feedback by continuously monitoring the contact sensor signal and comparing it against expected oscillation patterns. When the modulated air bearing causes the slider to approach and contact the disk, the feedback mechanism detects the characteristic signal change (such as a spike or deviation from the oscillation pattern) and uses this information to accurately determine contact events without saturation
2Measurement precision
If the slider is made to approach the medium repeatedly for contact detection, then contact detection sensitivity is improved, but the risk of slider burnishing increases
Solution Approach 1:
The patent applies preliminary action by using the modulated air bearing to bring the slider into contact with the disk in a controlled, oscillating manner before full contact detection is needed. The modulation creates gentle, repeated approaches that allow the detection system to identify contact events without requiring aggressive slider engagement, thereby reducing burnishing risk while maintaining detection sensitivity
Solution Approach 2:
The patent changes the parameter of air bearing stiffness through modulation, transforming it from a static support mechanism to a dynamic one that controls slider approach behavior. By modulating the air bearing pressure at a specific frequency, the system creates controlled oscillations that enable sensitive contact detection while limiting the force and duration of contact events, thus preventing slider burnishing
3Measurement precision
If AC power is supplied to the heater to cause oscillation in spacing, then contact detection capability is improved, but energy consumption increases
Solution Approach 1:
The patent applies periodic action by supplying AC power to the heater at a specific frequency (e.g., 100 Hz) to create oscillations in the slider-disk spacing. This periodic heating modulates the air bearing pressure, causing the slider to oscillate toward and away from the disk. The periodic nature of this action enables contact detection through characteristic signal changes during each oscillation cycle while limiting energy consumption to only the intervals when heating is applied, rather than continuous heating
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables robust and early detection of head-disk contact, reducing the risk of slider burnishing and improving contact detection sensitivity, particularly suitable for modulating air bearings, and can be integrated with traditional LFACH methodologies for enhanced performance.
Implementation Method 1
supplying AC power to a heater of the slider to cause oscillation in a spacing between the slider and the medium
Implementation Method 2
measuring an amplitude of DC response signals produced by a contact sensor of the slider
Data Source
AI summary
An apparatus comprises a slider configured for writing data to and reading data from a magnetic recording medium and for heat-assisted magnetic recording. The slider comprises a heater configured to receive an AC signal and to cause oscillation in a spacing between the slider and the medium, and a contact sensor situated on the slider and configured to produce a DC response signal. A detector is coupled to the slider and configured to measure an amplitude of a spike in the DC response signal, calculate a ratio between the spike amplitude and an amplitude of the DC response signal, and detect contact between the slider and the medium in response to the ratio exceeding a predetermined threshold.